Box with lid held by latches

A plain lidded box with rounded corners. The lid holds on latches.

Download .scad, set dimensions and wall width as you like.
If you change the wall width, consider tuning the latch.

Print instructions

Notes:
The .scad file has a parameter called clearence (misspelled clearance). clearence decides how tightly will the lid fits on the box.
If your printer prints slightly thicker than it should, either increase clearence or set an appropriate option in your slicer to hold the dimensions (in prusa-slicer, it's in Print Settings/Advanced/XY Size Compensation).